Ah, right.

When you record the guitar what happens is that Sonar records the dry signal which it then passes through Amplitube. So what is recorded is the dry guitar. This is good because it means if you want to change anything in Amplitube after you've recorded the audio you can without having to re-record the track from scratch because Amplitube is applied after the signal so it's non-destructive. That's basically how all plugins work in pretty much all DAWs.

So if you track using a Marshall and later think a Boogie might be better for the job, you can just load a Boogie into Amplitube and there you go. Want to remove the compressor? No problem, just delete it or turn it off and it's gone.

It's a bit of a guess, but it sounds like you might need to either record the MIDI Continuous Controller (CC) data that's working the volume pedal in a MIDI track with its output pointing to the Amplitibe volume pedal, or create an automation lane for the volume pedal and record the automation while recording the audio.

Then if you want to alter what the volume pedal is doing after you've recorded you can edit the MIDI or the automation. Because nothing is permanent, all the processing is done after the bare audio is recorded.

You could even record without using the volume pedal and draw an automation envelope in afterwards...

In order to do what you're trying to do, you need to click the R button to record enable the track and you also need to click the W button to write automation to the track. That way your foot pedal moves will be recorded at the same that your audio is recorded.

OK...problem solved.  I was able to record the MIDI data into a track and point the data to Amplitube.  The audio data was still recorded as "dry", but the MIDI data associated with the track made the "swells" happen in the recorded track.
 
Note - Amplitube had to be designated as a Synth instead of an FX in order for the MIDI data to be routed there.

While changing Amplitube to a synth does work. Starting with X3 it is not necessary. There is an "Enable MIDI Input" option in the VST2/3 drop down in the standard header for all plug-ins that can accept MIDI data.

Thanks...